Watching the bacteriophage N4 RNA polymerase transcription by time-dependent soak-trigger-freeze x-ray crystallography

Background: The two-metal-ion mechanism of the nucleotidyl transfer reaction by RNA/DNA polymerases has not been adequately elucidated due to lack of temporal resolution. Results: Soak-trigger-freeze x-ray crystallography revealed structures of natural, time-resolved intermediates of transcript initiation. Conclusion: First structural evidence shows that catalytic metal binds after the nucleotide and nucleotide-binding metal and right before reaction chemistry. Significance: Time-dependent soak-trigger-freeze x-ray crystallography can yield functionally relevant high resolution information to study enzyme reactions.